1. Field Of The Invention
The present invention generally relates to an apparatus for preparing stitch position-related data utilized by an embroidery sewing machine, and particularly to such an apparatus which automatically prepares stitch position-related data utilized by an embroidery sewing machine to embroider a predetermined area by forming stitches at respective stitch positions and thereby filling the area with the formed stitches.
2. Related Art Statement
The Applicant has filed U.S. patent application No. 07/523,379 on May 15, 1990, U.S. Pat. No. 5,179,520 in which he proposes an apparatus for automatically preparing stitch position-related data utilized by an embroidery sewing machine. The proposed apparatus includes (a) direction determining means, (b) block defining means, and (c) data producing means. The direction determining means determines a reference direction with respect to a predetermined area to be embroidered, based on outline data representative of an outline of the area. Specifically, the direction determining means determines as the reference direction, for example, the direction of a straight line approximating the predetermined area (hereinafter, referred to as the longitudinal direction of the area for the reason indicated later). The block defining means defines straight aid lines which are perpendicular to the longitudinal direction and respectively pass all the specific positions predetermined on the outline, and thereby dividing the area and the outline into blocks and segments, respectively.
In the case where the outline of a predetermined area to be embroidered includes a proper polygon, or a curved line which is not a polygon but is approximated by a polygon, the outline data may include sets of position data (e.g., sets of coordinate data in an X-Y orthogonal coordinate system) each of which is representative of a corresponding one of the vertices defining the polygon. In addition, in the case where the outline is approximated by a function such as a spline function, the outline data may include data representative of the function. If the outline consists of a polygon, the specific positions located on the outline may consist of the vertices of the polygon and the outline data may consist of the sets of position data representative of the vertices. If the outline is approximated by a function, the specific positions may consist of the points defined by the function and the outline data may consist of the sets of position data representative of the points.
The data producing means produces, based on the blocks resulting from the division of the area, stitch position-related data which is utilized by the embroidery sewing machine to form stitches and thereby fills the area with the stitches.
As is apparent from the foregoing, the proposed apparatus determines a straight line approximating a predetermined area to be embroidered, and utilizes the direction of the straight line, or longitudinal direction of the area, as an embroidering direction of the area in which direction to form stitches in the area. However, the apparatus divides the area into blocks by straight aid lines perpendicular to the longitudinal direction, irrespective of the profile or shape of the area or outline thereof. In the case where the area to be embroidered is approximated by a curved line or polygonal line (hereinafter, referred to as the central line of the area), there may occur a considerably large difference or deflection between the longitudinal direction of the area, and directions of the central line at individual positions or portions thereof (hereinafter, referred to as the central-line direction of the area). Obviously, the central-line direction serves as the more suitable embroidering direction than the longitudinal direction. Therefore, some of the blocks obtained by dividing the area by straight aid lines perpendicular to the longitudinal direction, may not appropriately reflect the central-line direction. Regarding a polygon shown in FIG. 28, the proposed apparatus determines as the longitudinal direction of the polygon, for example the direction of a straight line passing the most distant, or approximately the most distant, two vertices of the polygon (e.g., vertices P.sub.MIN and P.sub.MAX). However, as is seen in the figure, the polygon is more suitably approximated by an arc than the straight line defining the longitudinal direction. Therefore, the tangential direction of the arc as the central-line direction, serves as the more suitable embroidering direction. If, as shown in FIG. 28, the polygon is divided into blocks by straight aid lines perpendicular to the longitudinal direction, at least some of the blocks do not appropriately reflect the tangential direction of the arc. When the polygon is embroidered by alternately and successively connecting, with thread, between stitch positions provided on one of the two segments of each block which are opposed to each other in the direction perpendicular to the longitudinal direction, and stitch positions provided on the other segment of the each block, the embroidering direction for the at least some blocks (indicated at arrows in FIG. 28) will not appropriately coincide with the tangential direction of the arc in the zone of those blocks, thereby adversely affecting the quality of an embroidery as a whole formed in the polygon.